MFOS Sound Lab Mini-Synth PLUS Eurorack Version

One of Ray Wilson's most popular projects, NOW AVAILABLE AS A EURORACK MODULE! An ALL-IN-ONE synthesizer voice to serve as the foundational module for Eurorack rigs!

This is a fully-featured synth voice that includes two Oscillators, LFO, VCF, AR Envelope Generator, Noise, VCA and Mixer.

The original Soundlab Mini-Synth was ported to the eurorack format by the very talented David Haillant, who stayed true to the vast majority of Ray's original design principles. There are a few differences between the original and this new eurorack version:

"The starting point of the conversion came from a practical frustration: like most MFOS designs, the original SLMS requires an extensive amount of hand wiring between the PCB and the front panel controls. Every pot, switch, and jack must be individually connected, resulting in a dense and error-prone cable bundle, especially for beginners. To eliminate this, I decided to design my own version, with all the controls — potentiometers, switches, and jacks — mounting directly onto a PCB. The choice for Surface Mount Components (SMT) instead of Through Hole Components was a practical solution if I wanted to keep everything on a single board. Then it appeared that the Eurorack format was a good candidate for this version of the SLMS : the circuit, originally designed to be operated by two 9V batteries is compatible with the Eurorack voltage levels and can be powered directly by a standard ±12V bus.

Converting the SLMS to Eurorack meant rethinking the panel layout from scratch, as the ergonomics of a no-wire design have to be resolved entirely at the PCB design stage. While not a direct copy of the original layout, I kept the overall philosophy intact: two rows, each section clearly labeled and organized in the same global way, and the use of switches to set the various modulations and configurations. The electric circuit itself is a faithful reproduction of Ray's work. Even the component references and test points are all kept and can be used as cross-references between the THT and the SMT versions. This is particularly useful when doing troubleshooting. I chose to use two dual NPN arrays instead of the four individual hand-matched transistors. As these arrays share the same package, they are closely matched and have good thermal coupling.

Finally, two improvements, originally suggested by Ray himself, have been integrated. The first is the enhanced noise generator circuit. The noise transistor is intentionally left in through-hole format (TO-92, with footprints for both CBE and EBC pinouts). This gives the builder the freedom to experiment, as different transistors produce different noise characteristics. The second improvement is the redesigned VCO sync circuit — the original sync was noticeably weak, and this revision makes it significantly more reliable. It also improves the overall tracking on VCO2. I also added a "Hi Freq" trimmer on both VCOs... I think it's an improvement that I got from the Mk2 VCOs. It's not listed in the original SLMS extras nor in the PLUS.”

For the synthCube version, we chose to stay with David's classic panel design in FR-4 material with a unique 'bubble' texture, and color-coded the functional sections using color-cap knobs and color-matched pot, jack and switch washers. We offer the bundle that includes the panel and the PCB fully pre-soldered with SMT parts, a full kit, and assembled+tested versions with our one-year warranty. In addition to the SMT parts already soldered to the PCB, the full kit requires you to add a few thru-hole parts and the panel parts to finish the build before testing and calibration steps.

https://synthcube.com/mfos-sound-lab-mini-synth-plus-eurorack-version/